DR. HARISH AGING

1. wollega university SCHOOL OF GRADUTE STUDIES College of engineering and technology Department of mechanical engineering program ;master of manufacturing engineering title ; effect of aging on corrosion of aluminum alloy 6061 Course ; CORROSION AND SURFACE ENGINEERING Prepared by ;leta daba (wu1400111) Submitted to ;HARISH. K(ASSOCIATE PRO.)

2. Outline • Introduction • Objectives • Specific objectives • general objectives • Experimental work • Heat treatment procedure • Result • Conclusion

3. Introduction • Automated assembly • The following function are required in automated process line. • Sequence control • Safety monitoring • Quality control

4. Automated Assembly SystemsAssembly involves the joining together of two or more separate parts to form new entity which may be assembly or subassembly.Automated assembly refers to the use of mechanized and automated devices toperform the various functions in an assembly line or cell.Automated assembly system performs a sequence of automated operations tocombine multiple components in to a single entity which can be a final product orsub assembly. • Automated assembly technology should be considered when the followingcondition exists. • High product demand • Stable product design • The assembly consists of no more than a limited number of components. • The product is designed for automated assembly.

5. Types of automation assembly system • According to physical configuration • In line assembly machine • Dial type assembly machine • Carousal assembly system • Single station assembly machine CONT….

6. 1.2 OBJECTIVES • 1.2.1 OBJECTIVE • The objective of the present investigation is to indicate how certain simple but important variations in the thermal processing, such as the aging parameters, as well as differences in solution pH affect the corrosion characteristics of 6061 AA. It also aims to investigate the boundaries of IGC zone and pitting zone in order to have a clear picture about the localized corrosion behavior of this alloy. • 1.2.2 SPECIFIC OBJECTIVES • To investigate the boundaries of IGC zone & • Pitting zone

7. 2. Experimental work 3.1 Materials • The study was carried out on 10 mm thick flat plates of 6061 AA received in the peak-aged T6 temper. • The chemical composition is shown in Table 1. The plates were cut into samples of 10 mm width and 15 mm in length by electric discharge machine.

8. 3.2 Heat-treatment procedures In order to study the corrosion behavior and the microstructure changes, the samples were divided into two groups and were given heat treatment by two different procedures. For the first heat treatment procedure, solution heat treatment was carried out at 550°C for 2 hrs., followed by water quenching. . Some of these specimens were tested in the as quenched condition and the other specimens were artificially aged. On below table at three aging temperatures (140, 185, 225°C) for different aging times as summarized

9. Fig1.4 Heat treatment applied according to the first heat treatment procedure. Fig1.5 Heat treatment applied according to the second heat treatment procedure.

10. Hardness testing • The Vickers hardness number was measured for the samples heat treated according the first procedure • The samples were ground on SiC grinding papers from 240 till 600 grade, followed by polished on polishing lapped clothe using 1 µm diamond suspension. Load of 5 kg was applied for hardness measurements and the time of loading was 30 Seconds. Ten indentations were made on each specimen and the average hardness values were calculated. • Corrosion testing • Prior to corrosion behavior studies, samples were ground on SiC grinding papers from 240 till 1000 grade, followed by polishing on polishing lapped clothe using 1 µm diamond suspension. • Immersion corrosion test • Immersion in an acidified sodium chloride solution consisting of 30 g NaCl and 10 ml HCl per liter of double distilled water for 24 hr. • Electrochemical corrosion testing

11. Results • Hardness measurements;Age hardening curves obtained by hardness measurement of the alloy 6061 specimens after artificial aging of samples at 225, 185 and 140 °C for different times are shown in Fig.4.1. • This diagram shows the typical behavior of a precipitation hardening alloy, in which hardness first increases up and then decreases with time. • The age hardening behavior was influenced by the aging temperature in the usual manner:. Fig 4.1 Variation of hardness as a function of aging time for samples aged at 225, 185 and 140 °C after solution heat treatment at 550 °C for 2 hrs.

12. Cont… 1850c Immersion corrosion test Results of cross sectional examination of the alloy specimens, after immersion corrosion test, using optical microscope, indicated strong dependence on the heat treatment route 1400c Fig.4.2.Metallographic cross-section of water quenched specimen after immersion corrosion test Fig.4.3. Results of cross-sectional examination by optical microscopy for corroded specimens after different aging parameters.

13. Conclusions The results obtained from the present work indicate significant role of the aging parameters on the corrosion behavior of alloy 6061 AA quenched in ice – water after solution heat treatment. The following conclusion was made The maximum hardness values were obtained after aging for 17, 330, 11400 minutes at 225, 185, 140 °C, respectively. No significant differences in the peak hardness values were observed. The over aging effects are attained more rapidly with increasing aging temperature from 140 to 225 °C. For all aging conditions, testing in alkaline solution NaOH changed the slope of the cathodic polarization curves, increased the limiting cathodic current densities, shifted Ecorr in the active direction and increased the corrosion current densities Icorr compared to those in the neutral NaCl solution.